Dumbbell



FIG. 1 is a perspective view of the dumbbell of my design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a right side elevational view thereof, with the left side elevational view being a mirror image thereof; and,

FIG. 4 is a front elevational view thereof, with the rear elevational view being a mirror image thereof. 

The ornamental design for a dumbbell, as shown and described. 